string_more

string_more extends String and str with two utility traits:

• StringExt for in-place editing on String
• StrExt for the corresponding immutable operations on string slices

The crate focuses on small, allocation-aware helpers for padding, editing, boundary handling, and simple text analysis.

Installation

cargo add string_more

or add it manually:

[dependencies]
string_more = "0.4"

See CHANGELOG.md for release notes and breaking changes.

Quick Start

use std::collections::BTreeMap;use string_more::{StrExt,StringExt};let centered = "rust".center('-',2);assert_eq!(centered,"--rust--");letmut value = String::from(" rust\t");
value.expand_tabs_in_place(2);
value.trim_in_place();assert_eq!(value,"rust");assert_eq!("🦀rust".truncate_to_chars(2),"🦀r");assert_eq!("foobar".common_prefix("foobaz"),"fooba");let frequencies = "Hello".byte_frequencies::<BTreeMap<_,_>>();assert_eq!(frequencies[&b'l'],2);

API Notes

• StringExt mutates String in place.
• StrExt leaves the original value unchanged. Most transformation methods return a new String, while some analysis and slicing helpers return borrowed &str results.
• Most text operations are based on Unicode scalar values (char), not grapheme clusters.
• Methods that accept indices use byte offsets and require valid char boundaries.
• Most text-like inputs accepted by the API can be passed as char, &str, or String through the sealed EncodeUtf8 trait.

Frequency Example

char_frequencies counts Unicode scalar values, while byte_frequencies counts UTF-8 bytes:

use std::collections::BTreeMap;use string_more::StrExt;let s = "·x·";let char_frequencies = s.char_frequencies::<BTreeMap<_,_>>();assert_eq!(char_frequencies[&'·'],2);assert_eq!(char_frequencies[&'x'],1);let byte_frequencies = s.byte_frequencies::<BTreeMap<_,_>>();assert_eq!(byte_frequencies[&0xC2],2);assert_eq!(byte_frequencies[&0xB7],2);assert_eq!(byte_frequencies[&b'x'],1);

Overview

In-place editing with StringExt

• trim_start_in_place, trim_end_in_place, trim_in_place
• fill_start_in_place, fill_end_in_place, center_in_place
• pad_start_to_in_place, pad_end_to_in_place, center_to_in_place
• enclose_in_place
• expand_tabs_in_place
• strip_prefix_in_place, strip_suffix_in_place
• truncate_to_chars_in_place
• shift_in_place
• replace_in_place

use string_more::StringExt;letmut s = String::from(" foobar\t");
s.expand_tabs_in_place(2);
s.trim_in_place();
s.strip_prefix_in_place("foo");
s.enclose_in_place("[","]");assert_eq!(s,"[bar]");

Immutable helpers with StrExt

• fill_start, fill_end, center
• pad_start_to, pad_end_to, center_to
• enclose
• expand_tabs
• truncate_to_chars
• shift
• common_prefix, common_suffix
• longest_common_substring
• levenshtein_distance, hamming_distance
• char_frequencies, byte_frequencies
• next_char_boundary, previous_char_boundary
• join

use string_more::StrExt;assert_eq!("42".pad_start_to(5,'0'),"00042");assert_eq!("foobar".common_suffix("quxbar"),"bar");assert_eq!("sparrow".longest_common_substring("crow"),"row");assert_eq!(", ".join(["one","two","three"]),"one, two, three");

Selected Methods

Padding and enclosure

use string_more::{StrExt,StringExt};assert_eq!("Hello".fill_start("-",3),"---Hello");assert_eq!("Hello".fill_end("-",3),"Hello---");assert_eq!("Hello".center("-",3),"---Hello---");assert_eq!("42".center_to(5,' ')," 42 ");letmut s = String::from("Hello");
s.enclose_in_place("[","]");assert_eq!(s,"[Hello]");

Truncation and prefix/suffix helpers

use string_more::{StrExt,StringExt};assert_eq!("🦀rust".truncate_to_chars(2),"🦀r");assert_eq!("foobar".common_prefix("foobaz"),"fooba");assert_eq!("foobar".common_suffix("quxbar"),"bar");letmut s = String::from("foobar");
s.strip_prefix_in_place("foo");assert_eq!(s,"bar");

Boundary-aware indexing

use string_more::{StrExt,StringExt};assert_eq!("🦀".next_char_boundary(2),4);assert_eq!("🦀".previous_char_boundary(2),0);letmut s = String::from("HelloWorld!");
s.shift_in_place(5,1,' ');assert_eq!(s,"Hello World!");

Distances and substring search

use string_more::StrExt;assert_eq!("kitten".levenshtein_distance("sitting"),3);assert_eq!("karolin".hamming_distance("kathrin"),Some(3));assert_eq!("abc🦀".longest_common_substring("zzabcx🦀y"),"abc");

Safety and Coverage

This crate contains a small amount of unsafe code in the in-place mutation layer. The public API is covered by unit tests and doctests.

Contributing

Contributions are welcome! Feel free to open an issue or submit a pull request.

License

This crate is licensed under the MIT License. See LICENSE for more details.